Relatively few biotechnology products have been developed for treating wounds, such as partial-thickness burns. Most of the efforts have been directed towards chronic wounds, which do require a proper level of cellular growth factors for healing. The most conventional option of chronic ulcer treatment involves sharp debridement to remove all non-viable tissue, a non-weight-bearing regimen, moist saline dressings changed twice daily at which times the skin around the ulcer are cleansed with mild soap and water. Current advanced treatment for chronic ulcers include growth factors, skin replacement therapy, enzymatic and mechanical debridement to clean ischemic tissue, moist wound dressings, non-antibiotic cleansers, antibiotics (Edmonds et al., 2000, Lipsky and Berendt 2000, Moulin et al., 1998, Mandracchia et al., 2001). However, current therapy for chronic wounds is not completely effective. In fact, Regranex™ gel or Becaplermin (recombinant-human platelet-derived growth factor-BB), the only biological product in the market for chronic wounds (diabetic neuropathic ulcers) has shown only 9-23% improvement over placebo and 4-22% improvement over good ulcer care alone (Mandracchia et al., 2001, Edmonds et al., 2000, Wieman 1998). Thus, an effective treatment for wounds, chronic and/or acute, is needed.
Lactoferrin is an immunomodulatory human protein expressed throughout the body and found in highest concentrations in milk and colostrums. Recombinant human lactoferrin (RhLF) is a recombinant glycoprotein produced in Aspergillus niger (A. niger), a filamentous fungi. RhLF is structurally identical in all material respects to native lactoferrin and has a wide array of functions related to host defense mechanisms. For example, lactoferrin has been reported to activate natural killer (NK) cells, induce colony stimulating activity, activate polymorphonuclear neutrophils (PMN), regulate granulopoeisis, enhance antibody-dependent cell cytotoxicity, stimulate lymphokine-activated killer (LAK) cell activity, and potentiate macrophage toxicity.
Recombinant human lactoferrin has previously been described as being purified after expression in a variety of prokaryotic and eukaryotic organisms including aspergillus (U.S. Pat. No. 6,080,559), cattle (U.S. Pat. No. 5,919,913), rice, corn, Sacharomcyes (U.S. Pat. No. 6,228,614) and Pichia pastoris (U.S. Pat. Nos. 6,455,687, 6,277,817, 6,066,469). Also described are expression systems for the expression of full-length human lactoferrins (e.g., U.S. Pat. No. 6,100,054). In all cases, part of the teaching is expression of the full length cDNA and purification of the intact protein whose N-terminal, after processing of the leader peptide, is the amino acid glycine. Nuijens et al. (U.S. Pat. No. 6,333,311) separately describe variants of human lactoferrin but their focus is limited to deletion or substitution of arginine residues found in the N-terminal domain of lactoferrin.
EDTA (ethylenediaminetetraacetic acid) is a synthetic compound which has well known metal-binding characteristics. EDTA is most commonly used for chelation therapy, a treatment that involves repeated intravenous administration of EDTA to pull toxins from the bloodstream. EDTA administration is the medically accepted treatment for poisoning by heavy metals such as lead, mercury, arsenic and thallium and has been approved by the Food and Drug Administration (FDA) for this use.
EDTA has also been proposed as a treatment for heart disease. Proponents of chelation therapy for heart disease claim that EDTA, in combination with oral vitamins and minerals, helps dissolve plaques and mineral deposits associated with atherosclerosis. Although many Americans with heart disease have turned to EDTA chelation therapy to improve their condition, the FDA has not approved this therapy as an alternative treatment for heart disease. It is thought that EDTA chelation may help strengthen the immune system by sequestering impurities from the bloodstream.
The present invention is the first to develop a suitable delivery system to deliver lactoferrin to treat acute and/or chronic ulcers or other types of wounds, such as burns. Yet further, the present invention is the first to use lactoferrin in combination with a metal chelator to treat acute and/or chronic wounds.